Mars Probes Team Up to Save Stuck Rover

by SPACE.com staff | May 19, 2009 10:51am ET

Wheel slippage during attempts to extricate NASA's Mars Rover Spirit from a patch of soft ground during the preceding two weeks had partially buried the wheels by the 1,899th Martian day, or sol, of the Spirit's mission on Mars (May 6, 2009). Spirit took Credit: NASA/JPL-Caltech

NASA is
pulling out all the stops to try to get the mired Spirit rover out of the
Martian sand and rolling again.

NASA's
rover project team is using the Spirit rover and other spacecraft at Mars to
begin developing the best maneuvers for extracting Spirit from the soft Martian
ground where it has become
embedded.

The
possibility of the wheel being jammed was one factor in the rover team's May 7
decision to temporarily suspend driving
Spirit after that wheel stalled and other wheels had dug themselves about
hub-deep into the soil.

A
diagnostic test on May 16 provided some encouraging news: electrical resistance
in the left middle wheel is within the expected range for a motor that has not
failed.

"This
is not a full exoneration of the wheel, but it is encouraging," said John
Callas of NASA's Jet Propulsion Laboratory, Pasadena, Calif., project manager
for Spirit and its twin
rover, Opportunity. "We're taking incremental steps. Next, we'll
command that wheel to rotate a degree or two. The other wheels will be kept
motionless, so this is not expected to alter the position of the vehicle."

Another
reason to suspend driving is the possibility that the wheels' digging into the
soil may have lowered the body of the rover enough for its belly pan to be in
contact with a small mound of rocks.

The rover
team is using Opportunity to test a procedure for possible use by Spirit:
looking underneath the rover with the microscopic imager camera that is mounted
on the end of the rover's arm. This might be a way to see whether Spirit is, in
fact, touching the rocks beneath it.

Spirit and Opportunity have been trundling across the Martian landscape for more
than five years now.

NASA's Mars
Odyssey orbiter is also aiding in the Spirit recovery plan. As a result of
winds blowing dust off Spirit's solar panel four times in the past month,
Spirit now has enough power to add an extra communication session each day. The
Odyssey project has made the orbiter available for receiving extra
transmissions from Spirit. The transmissions include imaging data from Spirit's
examinations of soil properties and ground geometry.

Rover team
members are using that data and other information to construct a simulation of
Spirit's situation in a rover testing facility at JPL. The team is testing
different materials to use as soil that will mimic the physical properties of
the Martian soil where Spirit is embedded. Later, the team will test maneuvers
to get the rover free. Weeks of testing are anticipated before any attempt to
move Spirit.